One of the fastest-warming regions of the U.S. is the Southwest — and that region, plus the broader West, is stuck in its most expansive and intense drought of the 21st century.

Why it matters: Studies show that a warming climate is exacerbating the drought, and in some ways may be triggering it in the first place. That means the Southwest is drying out — and California's large wildfires could start as soon as next month.

• And one climate researcher says California's Sierra Nevada Mountains saw one of the fastest snow melt-outs in history this year.
• The drought situation is particularly severe in the Colorado River Basin and northern California. Scientists and public officials are warning that the California wildfire season is likely to be severe, due to the combination of dry vegetation and above-average temperatures.
• This one comes on the heels of the worst fire season in state history, which turned the skies above San Francisco a "Blade Runner" orange last year.

The big picture: Some parts of the world are already getting close to, or have slipped beyond, the Paris agreement'stemperature limit thatscientists warned about in a report last week.

• As Earth's temperatures tick upwards, closer to the Paris guardrail of 1.5°C (2.7°F) above preindustrial levels, some parts of the world are already warming by much greater amounts, from the Southwestern U.S. to the Arctic. These areas are seeing destructive impacts that are mounting.

Details: California's Sierra Nevada Mountains show what climate change can do as it worsens. The mountain snowpack, which provides 30% of the state's water supply annually, has vanished about two months ahead of schedule.

• Water runoff from snow melt has been paltry, and major reservoirs like Lake Oroville are running even lower than they did during the record drought from 2012-2016.
• Climate change is playing a key role in the drought, by boosting temperatures and increasing the loss of water to the atmosphere. Much of the snow went directly from frozen form back into the air, rather than melting into runoff.
• Warming is also thought to be leading to increasing chances of dry fall seasons in the Golden State and shortened rainy seasons, according to Daniel Swain, a climate researcher at UCLA and the Nature Conservancy.

Craig Clements, who studies wildfires at San Jose State University, warns that large wildfires typically not seen until late summer in California could occur this year as early as June. Vegetation is at near record dry levels for this time of year, he said.

• "We are starting off in a more dire situation than we typically would for June," Clements told Axios.

Context: The worsening drought and potentially devastating wildfire season is not an isolated occurrence for California and other Southwestern states.

• Climate studies have consistently shown that as the world continues to warm, the Southwest will become drier and hotter. This is worrisome, given the likelihood of increased stress on water resources amid a population boom in states such as Arizona and Nevada.
• Although it's interspersed with short intervals of wetter years, parts of the West, including California, are suffering through an emerging, human-caused "megadrought" that began in 2000.
• Studies show this drought, measured using soil moisture data and tree rings, is the second-worst in the past 1,200 years.

What they're saying: "This current drought has quickly accelerated, and is now on par (if not worse) than the extreme and in some cases record-breaking drought that occurred just 5 years ago in California," Swain said.

What's next: If the world does not steeply reduce greenhouse gas emissions starting in this decade, more areas will warm to near or above the Paris limits, until the global average arrives at that level as well.

• This threatens to unleash catastrophic impacts, such as the melting of parts of the Antarctic Ice Sheet.
• For now, the drought and likely severe wildfire season in the West offer an unfortunate preview of what may come next.

Go deeper:

Earth may temporarily hit Paris climate limit in next 5 years

A very, very, very dry future for the U.S. West

Drought stokes fears of severe fire season in West